This invention relates to environmental housings for electrical equipment and, more particularly, to an outdoor mounted all-weather enclosure for microwave radio transceivers.
PCT application WO 00/25485, published May 4, 2000, discloses a broadband wireless network invention by Berger et al. based on mesh topology having a plurality of wireless transceivers operating in the gigahertz range with the ability of adding and dropping data at each transceiver, as well as routing data between multiple wireless transceivers. Transceivers with switches are considered to be nodes, designed to select a transmission direction and a receive direction based upon the routing address of data packets to be sent and received. The selection of a transmission or receive direction is done instantaneously to accommodate short bursts of data packets arriving from nodes located at different directions or transmitted towards nodes located at different directions as defined by a scheduler of the MAC (media access control) layer.
PCT application WO 00/76088, published Dec. 14, 2000, discloses a scheduler and control algorithm for a system as described above. The scheduler is designed to efficiently allow implementation of mesh networks with IP packet data flow between the network nodes or backbone access points. The disclosed MAC protocol features transmission of synchronous schedule information in a control channel between the nodes to assign asynchronous variable length packet data slots in between the schedule information time slots. Available data slots are adaptively assigned by each recipient node to the data initiator node based on requested time slots by the initiator and the available time slots of the recipient.
The mesh topology networks described above operate in the multi gigahertz spectrum, i.e. microwave bands. In 1998, the FCC auctioned a large amount of the radio spectrum in the 27 GHz and 31 GHz bands for use in Local Multipoint Distribution Systems. Similar spectral bands were opened for use in Canada, Australia, New Zealand and Argentina. In Europe, the radio spectrum between 24.5 GHz and 26.5 GHz was also assigned for multipoint use. Many countries are in the process of opening different bands at the high frequency spectrum between 10 GHz and 40 GHz for use on a territorial basis rather than on a link per link basis, as in the past. This main difference of approach in licensing the radio spectrum enables the network operator to build a network, which covers a large topographical area and offers connectivity services to those customers in line of sight relation in the area. This is because millimeter wave transmission depends on line of sight between communicating transceivers. An arrangement of devices as described above is shown in PCT international patent application PCT/US00/15482, published Dec. 14, 2000.
Another type of radio system operating in the same spectral region is the point to multipoint network. Such a system employs a simpler MAC layer because of the broadcast nature of the downstream link and the polling of the upstream link. When the base station transmits in a certain frequency and time slot, all the customers in the sector except the one that receives information are blocked from receiving any information. In the upstream direction, only one customer can transmit at a certain time on a certain frequency.
For these types of communications systems, an object of the invention was to provide a rugged, durable, mast-mounted, all-weather radio housing. Such a housing must allow multiple directional beams of millimeter waves to be transmitted to nodes dispersed over wide angles, i.e. typically wider than 90 degrees, for line of sight communication between nodes.
The present invention is a fixed weather-tight enclosure, acting as a housing for a wireless node, including a microwave radio transceiver in an adaptive wireless network, such as a mesh topology network, capable of sending and receiving energy in multiple directions. The enclosure features an exterior shroud, having an elliptical cross section for shedding rain and snow. The overall appearance of the unit is almost egg-shaped, with a maximum dimension of about one-half meter. The enclosure protectively shields an exposed bullet shaped radome, similar to the type used on aircraft fuselages, pointed in line of sight relation to one or more other similar enclosures. Other enclosures communicate with each other on the same basis. Each enclosure provides environmental protection for a passive curved microwave radio refractive lens acting as a non-resonant antenna capable of transmitting and receiving in selected directions. This lens receives and refractively bends electromagnetic energy from or to a curved array of feed ports, proximate to the curved surface of the lens element, so that the antenna can selectively transmit radiation in desired directions, depending upon the particular radio frequency feed ports providing energy to the refractive element. The radome provides sufficient clearance to allow passage of beams or signal lobes over various angles typically exceeding 90 degrees in spread with beam widths of a few degrees. A microwave radio transceiver, the microwave refractive lens, the array of feed ports and support circuits all fit within the enclosure.
The enclosure is mounted on a mast by a bracket attached to heat sink fins on the rearward portion of the shroud. The bracket allows angular adjustment, both horizontally and vertically, of the pointing direction of the radome.
The shroud has two major compartments. A first compartment is the body which houses the supports for the microwave lens, switches, fan and heater, and the feed element array. The second compartment surrounds the first compartment and has the power supply, transceiver, motherboard, and a second radio for local communication, control, and utility circuits. The second compartment, being made of thermally conductive metal, preferably aluminum, defines heat sink fins in the rear of the shroud body. A small door, also in the rear of the shroud body, gives access to power and data cables, as well as wires, leading into the interior of the second compartment. Access to the unit power supply is through the same small door so that disassembly of the entire unit is not needed to check or repair the power supply.
Within the first compartment, an electrical heater, a fan and a control circuit operate to circulate warm air within the radome with sufficient capacity to avoid accumulation of frost or ice on the exterior surface of the radome. An interior partition within the shroud provides support for the base of the radome. The partition has a central aperture allowing the microwave lens to extend from the rearward portion of the shroud into the radome. Also with the first compartment is a support frame having spaced apart sockets for securing the microwave lens. The lens, in the preferred version, is ball shaped and has spaced apart protuberances on opposite sides of the ball shape, which fit into the sockets in an interlocking manner.
A network of similar enclosures mounted on masts or high locations relay data among themselves according to schedules in a control channel transmitted with the data. Enclosures having several other enclosures in a line of sight relation may select the direction of transmission, depending on addresses contained within the control channel of information received. The protective shroud in each enclosure helps establish an all weather-operating environment for mast mounted microwave transceivers.